The equine foot is a complex structure, with the forelimbs and hindlimbs working together to support the body and carry its load. Incorrect or imbalanced anatomy can lead to lameness, which is a common problem in the horse. Proper balance and symmetry throughout the body are important for good biomechanics, and these can be assessed with an anatomical chart.
The human finger has two large triads of vein, artery and nerve (VAN) that supply the primary blood supply and innervation to each digit. In horse cross sections, there are between five and seven distinct triads in the phalangeal region. This is more than the two VANs expected if the limb were truly monodactyl, but less than the 10 VANs that would be expected in a pentadactyl taxon.
In fetal horses, the hoof has four distinct infoldings on the ventral side and is smooth without subdivisions on the dorsal side. These infoldings are softer than the dorsal horn and help support and protect the coffin bone from external forces, especially shear forces. In addition, the keratinous hoof wall is rich in germinating tissue that grows continuously over the dorsal surface of the distal phalanx, forming a thick layer of keratin called a periople. The periople adheres to the dorsal keratinous layer and helps prevent the underlying coffin bone from drying out.
A horse’s forelimbs are made up of the fetlock, pastern and hock joints. The fetlock is the most similar to the knee joint of humans, while the hock is more like the heel. The hock is a very strong joint that supports the horse’s weight, and it is difficult to damage by jumping or running.
As a result, it is more difficult to diagnose hind limb problems than forelimb ones. The anatomy of the hind limb is more complicated, and the musculature is much greater. This makes it harder for a trained examiner to feel and visualize the deeper structures.
There are several different types of articulation in the horse’s knee and hock joints, but the most important are the two arches that form the hind leg. These are formed by the stifle (or knee) and the gaskin, which is found a hand’s distance down the limb from the stifle joint. The hind leg also has a flexor tendon that connects the fetlock to the anklebone. This flexor tendon is used for movement and to absorb shock. It is protected by the frog and is very important for proper leg function. The frog is also the site of the horse’s sweat glands. The horse’s nostrils are lined with sensitive, pliable cartilage that can open and close to regulate airflow as needed. This flexibility helps the horse breathe in hot or cold weather and adapt to environmental conditions. It also allows the horse to use its nose to find food and water. This adaptation may be why horses can travel long distances in a short amount of time. The nostrils can be wide and flat or narrow and curved.